In the "Prologue" to Antigone, Antigone tells her sister Ismene that "it is the dead not the living, who make the longest demands."  Antigone is referring to the laws of the gods who hold that family members must honor their dead with, among other things, a proper burial.  Antigone tells Ismene that she can follow the laws of men if she wants, but the dead challenge the living to follow the proper moral code of the gods.  Afterwards, Antigone says, "We die forever," meaning that the afterlife is everlasting and the actions that one performs in the mortal world affect the nature of one's existence in the afterlife, which goes on forever.  Antigone is warning Ismene to consider the decision that she is making in following Creon's order because the mortal world is only temporary.